The present invention relates to packaging of stacks of multiply articles made of paper or the like, in particular a stack of folded napkins made of tissue paper material.
Nowadays, there are machines which package automatically stacks of multiply articles made from paper or like material. The above mentioned machines feed the stacks of multiply articles to a conveying line, which space them out and conveys them, stepwise, to a packaging device. The packaging device is operatively connected to a feeding line which feeds sheets for wrapping the stacks.
More precisely, the packaging devices include means for:
compacting the stack to be packaged,
conveying longitudinally the stack, so that it hits a relative packaging sheet, previously placed and held vertically by means connected to the above mentioned feeding line, until the stack, wrapped within the packaging sheet along three subsequent sides of its contour, is introduced between facing runs of a pair of endless conveying means,
welding the overlapped edges of the wrapping sheet in the region of the fourth side of the stack contour.
Folding means, situated downstream of the above mentioned device, fold the wrapping sheet over the front and rear heads of the stack.
Then, traditional welding means weld the flaps made by the folding means.
According to a known solution, the means for compressing the stack to be packaged include a base plate, onto which the stack is fed, and an upper pressing plate, which is movable vertically to compact the stack.
The base plate and the upper pressing plate are situated close to the wrapping sheet which is fed vertically.
Actually, the base plate includes a portion, which is movable between a position slightly backward with respect to the vertical plane on which the wrapping sheet is fed, and a forward position close to the sheet.
The conveying means include also a pair of platens moving longitudinally and receiving the stacks to be transferred to the conveying means.
The stack to be packaged, fed onto the base plate, is pressed by the upper pressing plate and subsequently, acted on by a conventional pusher member, which transfers it longitudinally, so as to hit the packaging foil, previously situated vertically.
In suitable time relation, the movable platens, with the previously fed stack still situated therebetween, are moved to a backward position, close to the wrapping foil, so as to receive the forward moving stack, which thus hits the wrapping foil.
Obviously, the distance between the movable platens is equal to the distance between the base plate and the upper pressing plate which compact the stack.
Due to the forward movement, the stack, which hits the wrapping foil, is inserted between the movable platens and, at the same time, moves the previous stack toward the conveying means.
Then, the movable platens are moved to a forward position, so that means for folding and welding the overlapped edges of the wrapping foil can be operated.
According to another known solution, the stack, which hits the wrapping foil, is introduced between a pair of auxiliary conveying members situated close to the wrapping foil, suitably distant therefrom.
The auxiliary conveying members are in line with the conveying means situated downstream, and distant therefrom by a section which allows to introduce the means for folding and welding the overlapped edges of the wrapping foil.
In this case, the stack to be packaged, fed onto the base plate, is compacted by an overlaying pressing plate and then transferred longitudinally by a pusher element, so as to hit a wrapping foil and to be introduced between the auxiliary conveying means, which transfers the partially wrapped stack to the conveying means, situated downstream.
Actually, the operation speed of the above described devices does not satisfy different needs, due to the complexity of the movements.
Moreover, especially in the second of the described solutions, the wrapping foil is not tightened perfectly, which results in not perfectly square packages.
Further, the above described devices are complex in their construction and are poorly functional, which derives particularly from the use of the auxiliary means for introducing stacks into the conveying means.
Consequently, the costs increases and so does the probability of irregular operation.
The object of the present invention is to propose a method which allows to package stacks of multiply articles, with a high operation speed, maintaining at the same time perfect tensioning of the wrapping foil.
Another object of the present invention is to propose a method which minimizes the inoperative periods and reduces the stroke necessary to transfer the stack from the pressing means to the pair of conveying means.
A further object of the present invention is to propose a device which allows to package stacks of multiply articles, with a high operation speed, maintaining at the same time perfect tensioning of the wrapping foil.
A still further object of the present invention is to propose a device which carries out the above packaging by a very simple and functional structure.
The above mentioned objects are obtained in accordance with the contents of the claims.